Effects of nutrient solution pH on the survival and transmission of Clavibacter michiganensis ssp. michiganensis in hydroponically grown tomatoes

Abstract

The effect of pH on the survival of Clavibacter michiganensis ssp. michiganensis and its transmission via roots of tomato in hydroponic culture was studied in laboratory and greenhouse experiments. In a laboratory experiment, C. m. ssp. michiganensis could not survive for 24 h in nutrient solutions with a pH of 4´0 or 4´5, while 1, 14, 51 and 62% of inoculum survived at pH 5´0, 5´5, 6´0 and 6´5, respectively. When tomato plants were inoculated with C. m. ssp. michiganensis through wounds on the stems, the bacteria moved downward from the inoculation site to the roots and infectious bacteria were released from the roots into the nutrient solution. Of two pH regimes tested in greenhouse nutrient-film technique (NFT) culture, the C. m. ssp. michiganensis population was significantly lower in pH 5´0 than in pH 6´5 in most sampling data. In treatments in which C. m. ssp. michiganensis was introduced by transplanting two root-inoculated plants, significantly more plants developed canker at pH 6´5 (34 out of 48 plants) than at pH 5´0 (11 out of 48 plants). When the bacterium was introduced by transplanting two stem-inoculated plants at pH 6´5, seven out of 24 plants developed canker. The potential of pH manipulation in controlling tomato bacterial canker in hydroponic culture is discussed.

PM 7/42 (3) Clavibacter michiganensis subsp. michiganensis

“…Detection of latent infections of C. michiganensis subsp. michiganensis in nursery plants with no evident symptoms is erratic since the incidence of infections and the distribution of the pathogen (in roots, stem or leaves) can be variable depending on the culture conditions of the plantlets, for example whether or not they have been grafted or whether re‐circulating water has been used for irrigation (van Vaerenbergh et al ., ; Huang & Tu, ; Kawaguchi et al ., ; Xu et al ., ). A method for testing nursery plants is presented in Appendix , although it has not yet been fully validated.…”

PM 7/42 (2) Clavibacter michiganensis subsp. michiganensis

“…Detection of latent infections of C. michiganensis subsp. michiganensis in nursery plants with no evident symptoms is erratic as the incidence of infections and the distribution of the pathogen (in roots, stem or leaves) can be variable depending on the culture conditions of the plantlets, for example, whether or not they have been grafted, or whether recirculating water has been used for irrigation (van Vaerenbergh et al ., ; Huang & Tu, ; Kawaguchi et al ., ; Xu et al ., ). A method for testing nursery plants is suggested in Appendix for information, although it has not yet been fully validated.…”

Impact of Good Seed and Plant Practices on the Incidence of Bacterial Canker in a Commercial Tomato Nursery

“…Furthermore, the secondary spread of Clavibacter michiganensis subsp. michiganensis in the commercial nurseries or greenhouses can occur via contaminated equipment used for clipping or grafting practices and workersʼ hands during the tomato chain production 10 . Thereby, the best way to avoid the disease in the greenhouses is by maintaining the seeds and transplants free of the pathogen 2 .…”